The “Relative Feed Value” of fodder

The largest operating cost in a livestock production enterprise is feed. With pasture farming, the true cost of feeding an animal is often disguised in a mixture of fertiliser, soil damage repair, re-grassing, crop rotation, fencing, weed control, capital maintenance and labour costs. Minimising this cost while still achieving the best result is a challenge, as both under and over feeding incurs financial penalties. Underfeeding results in reduced animal performance and profitability, while overfeeding is wasteful resulting in financial (grading) penalties. Balanced, measured animal feeding and nutrition are crucial to the profitability of the livestock enterprise.

Laboratory analysis of the composition of feed or forage (not once but continuing over time) is essential to assess the nutritive value of forage. A typical feed analysis includes measurements of some important quality attributes or parameters (such as crude protein, fibre, digestibility, energy) used to define nutritive value.

As with all such data, the farmer then needs to apply common sense and judgement to the information received to match the farm’s livestock requirements with the farm plan, market conditions, cash flow, environmental factors, capital and labour resources to develop an optimised model for that particular farm. They don’t call it farm management for nothing!

Ascertaining the Relative Feed Value of forage and supplemental feeds is one way in which a comparative index can be established to measure feed performance values.

Measured against an index of 100 for full bloom Lucerne the relative feed value of other feeds such as silage, hay and fodder can be measured as to their overall nutritional benefit in value to livestock. While relative feed values vary over time, it is at the time when the forage is to be supplied to livestock which is the most critical comparative point.

While quality dairy hay would be expected to fall in the range of 130% to 150% (against a full bloom Lucerne base of 100%) sprouted barley, if it is to provide value both in terms of bulk and nutrition should exceed at least twice the Lucerne base.

Based upon nutritional analysis undertaken by Massey University on Fodder NZ grain samples we have calculated the relative feed value percentage of the Fodder NZ samples for day five at 249% and a six at 250% compared to a crop of full bloom lucerne. On any conservative estimate, these results indicate the significant feed value advantage to be gained by farmers through feeding high-quality and highly nutritious Fodder NZ sprouted fodder.

Background

In the last week of February 2017, we extracted samples of sprouted barley from our production growing room for scientific analysis. The samples were weighed, frozen and freeze-dried before being sent to Massey University on 1 March 2017.

Massey University’s nutrition laboratory applied a number of industry-standard tests to the samples provided and on 5 May 2017 issued their final report. A full copy of this report can be found here.

The sample selected compared the dry un-sprouted grain on day zero with sprouted grain on days 3, 4, 5 and 6. All samples came from the same growing room and there were no changes to the production program between the days from which the samples were extracted.

The nutrition laboratories findings are summarised in the table below.

In order to understand the significance of the numbers presented above, and those that we have derived in the further table below is important to understand the meaning and significance of the nutrition and feed terms used. Briefly, these are:

• ADF (acid detergent fibre): This is the fibre measurement extracted with acid detergent in a technique employed to help appraise the quality of forages. ADF is highly correlated with cell wall digestibility. The higher the ADF, the lower the digestibility or available energy. As the ADF percentage in forage negatively relates to digestibility, ADF is used to calculate energy values. Low ADF forages are usually preferred because it means they have higher net energy. As a plant matures, ADF increases.
• Ash: Ash is the mineral matter present in the feed. It is measured by burning the sample at a high temperature until all organic matter is burned weighing the residual (ash).
• Protein: crude protein is a total protein in the feed. To calculate the protein percentage, the feed is first chemically analysed for nitrogen content. Since proteins average approximately 16% nitrogen, the percentage of nitrogen in the analysis is multiplied by 6.25 to give the crude protein percentage.
• Crude fibre: This is the portion of the plant composed of polysaccharides such as cellulose, hemicellulose and lignin. They serve as structural and protective parts of the plants; generally high in forages and low in grains. When the crude fibre content is higher, the energy content of the feed is lower as crude fibre is considered indigestible. Crude fibre increases with the age or growth of the plant.
• NDF (Neutral detergent fibre): NDF is a measurement of fibre after digestive in a non-acidic, non-alkaline detergent as an aid in determining the quality of forages. It contains the fibres in ADF plus hemicelluloses. NDF gives bulk or fill to the diet and is negatively correlated with feed intake. As NDF can be used to predict intake, it is one of the most valuable analysis to have conducted on forages for most sheep and beef rations. Low NDF is usually desired. As maturity of the plant at harvest increases, cell wall content of the plant increases resulting in an increase in NDF.
• DM (Dry Matter): The dry matter percentage is that part of the feed which is not water. Feed values and nutrient requirements for ruminants are expressed on a dry matter or moisture free basis to compensate for the large variation in moisture content of feed is commonly fed to cattle.
• DE (Digestible energy): Expressed in megajoules per kilogram, digestible energy is a prediction calculation that provides an indication of the actual amount of energy from the feed the can be available for use by the animal.
• GE (Gross energy): Expressed in kilojoules per gram, gross energy refers to the amount of energy contained in the energy-yielding nutrients of foods (carbohydrate, fat and protein). It is calculated as the energy released as heat when the particular food is completely combusted under a scientifically defined process (known as a bomb calorimeter).

Why do we need Relative Feed Values

From the above data, on its own, it is difficult to ascertain an overall value of the feed value of the sprouted barley. Some of the measurement factors on their own given indication of a partial picture and while providing guidance to a person familiar with the particular measurement standard (such as dry matter) they do not provide a holistic view of the overall benefit of the product when compared to other feed sources. This has long been a criticism of the “dry matter” standard; often the first question farmers ask about a livestock feed source.

As progressive farmers are aware, dry matter on its own does not provide an indication of nutritional value, digestibility or energy transfer. Even with the production of information such as calculated values for digestible energy and gross energy, there is a gap in the reader’s knowledge as to how much better or worse feed forage is compared to something else.

In the United States and Canada, it is for this reason that the development of relative feed value (RFV) has become an important measurement standard. RFV was developed primarily for use with legume or legume/grass forages combining digestibility and intake estimates into one number for an easy and effective way to identify and market quality hay across North America.

RFV is expressed as a percentage compared to full bloom Lucerne at 100% RFV. RFV’s above 130 are considered good dairy quality hay. The higher the value the better with a target around 150 being considered desirable.

Relative feed value is calculated using digestible dry matter and dry matter intake calculations. These are able to be derived from data analysis reported on the fodder NZ sample, submitted to the Massey University nutritional laboratory using the ADF and NDF data along with industry based adjusters.

Analysing the Massey University data and after calculating DDM%  &  DMI based upon the sprouted grain sample we arrive at the relative Feed Value of the submitted sample of 249% for day 5 and 250% for day 6. While a higher RFV was calculated for days 3 & 4 the development of the sprout from grain to a plant that was able to be economically consumed and utilised by an animal had not been reached. This is consistent with our expectations of teh balance between a nutritional maximum and a practical level of dry matter for consumption.

For interest we set out the relative calculations below: